One common method for printing images on a receiver member is referred to as electrography. In this method, an electrostatic image is formed on a dielectric member by uniformly charging the dielectric member and then discharging selected areas of the uniform charge to yield an image-wise electrostatic charge pattern. Such discharge is typically accomplished by exposing the uniformly charged dielectric member to actinic radiation provided by selectively activating particular light sources in an LED array or a laser device directed at the dielectric member. After the image-wise charge pattern is formed, the pigmented (or in some instances, non-pigmented) marking particles are given a charge, substantially opposite the charge pattern on the dielectric member and brought into the vicinity of the dielectric member so as to be attracted to the image-wise charge pattern to develop such pattern into a visible image.
Thereafter, a suitable receiver member (e.g., a cut sheet of plain bond paper) is brought into juxtaposition with the marking particle developed image-wise charge pattern on the dielectric member. A suitable electric field is applied to transfer the marking particles to the receiver member in the image-wise pattern to form the desired print image on the receiver member. The receiver member is then removed from its operative association with the dielectric member and the marking particle print image is permanently fixed to the receiver member typically using heat, pressure or and pressure. Multiple layers or marking materials can be overlaid on one receiver, for example, layers of different color particles can be overlaid on one receiver member to form a multi-color print image on the receiver member after fixing.
In the earlier days of electrographic printing, the marking particles were relatively large (e.g., on the order of 10-15 μm). As a result the print image had a tendency to exhibit relief (variably raised surface) appearance. Under most circumstances, the relief was considered an objectionable artifact in the print image. In order to improve image quality, and to reduce apparent relief, over the years, smaller marking particles (e.g., on the order of less than 8 μm) have been formulated and are more commonly used today. Relief is not always undesirable but to date printing documents with to form one or more optical elements using electrographic techniques has not been done as described.